The thesis is devoted to the synthesis of complex substituted calcium phosphates containing polyvalent metal ions (Cu2+, Zn2+, Cs+ or Sr2+) and investigation of their chemical, thermal, mechanical and biological properties. Composites based on apatite related phases were created and future practical applications of synthesized compounds were discussed.
Particularities of formation of Cu2+, Zn2+ та Cu2+/Zn2+-containing apatite and whitlockite related calcium phosphates were firstly investigated using two synthetic routs (wet precipitapion and sorption on nanosized complex calcium phosphates). The general trends of phosphates phase formation were established at the initial molar values Са/Р = 1.67, CО32-/РО43- = 1, Ca/MII = 50 і 100 and Ca/(Cu+Zn) = 50) at 20 °С under wet precipitation conditions of system Na+-Ca2+-M2+-NO3--CO32--PO43- (M2+ – Cu2+, Zn2+). According to IR and XRD data, these samples belonged to apatite type phase. B-type substitution of phosphate by carbonate was observed. Phosphates (2 % wt. bivalent metals) were obtained as spherical particles with sizes in the range 10-30 nm.
The influence of microwave radiation (during 30 minutes) on phosphates characterizations was firstly investigated. Annealing at 700 С resulted in the formation of crystalline products (apatite related calcium phosphates) and aggregation of particles.
Copper- and zinc-containing calcium phosphates were also obtained via sorption of bivalent metals nitrate solutions with different concentrations (0.002, 0.02 and 0.1 mol/l) and feather annealing at 700 °C. The pre-synthesized Na+, CO32-–containing calcium phosphate was used as a matrix for sorption.
It was found that content of sorbed bivalent metal ion increased (max to 6 % wt) with growt of its concentration in the initial solution. Formation of two phases realized depending on amount of precipitated bivaled ion. Apatite related phosphates were obtained at initial concentration с(М2+) = 0.002 mol/l while whitlockite related phosphates formed at с(М2+) = 0.1 mol/l.
For the first time, cesium ions incorporation in calcium phosphates framework was investigated during formation of phosphate matrix (wet precipitaton) and sorption on crystal matrixes of apatite and whitlockite related calcium phosphates. Apatite phases containing 0.2-1.5 % wt Cs+ were obtained by precipitation in system M+-Ca2+-Cs+-PO43--CO32--NO3- (M+ – Na, K) (molar values CO32-/PO43- = 1.0 and 2.0, Са/Р = 1.67).
It was found for carbonate free system M+-Ca2+-Cs+-PO43--NO3- (M+ – Na, K, molar ratio Са/Р = 1.67, CО32-/РО43- = 0, М+/Cs+ = 1.0 and 2.0) that addition of Cs+ cations stabilized the phase based on -Са3(РО4)2 in mixture with whitlockite related calcium phosphate. Formation of single phase calcium phosphate of whitlockite type (-Са3(РО4)2) was observed only in the presence of potassium cations at К+/Cs+ = 2.0.
Sorption properties of synthesized nanosized Na+- and K+-containing calcium phosphates (apatite and whitlockite types) were investigates relative to Cs+ ions for its nitrate solution of different concentrations (0.05, 0.1 and 0.25 mol/l). It was demonstrated that the amount of sorbed cesium increased with growth of its concentration in initial solution. The phase composition of calcium phosphates after sorption and heating to 700 °С depended on type and chemical composition of initial crystal matrix. Strontium containing phosphates were synthesized by wet precipitation method in the solutions of system M+-М2+-PO43--CO32--NO3- (M+ – Na, K, M2+ – Sr, Ca/Sr) at molar values M2+/Р = 1.67, CO32-/PO43- = 0 and 1.0. It was established that adition of Ca2+ ions in initial solutions caused an increase of degree of Sr2+ binding (to 90 % wt.) in the form of whitlockite and apatite type phosphates.
Antimicrobial properties of nanosized chemically modified apatite-related calcium phosphates (Na+,CO32-–НАР, Na+,Zn2+,CO32-–НАР and Na+,Cu2+,CO32-–НАР) against strains Staphylococcus aureus, Pseudomonas aeruginosa and Streptococcus pyogenes were investigated. Inhibitory effect of samples in the form of slurries (5-20 mM) on growth of conditionally pathogenic microorganisms was established.
Influence of particles sizes on antimicrobial properties of phosphates was found on the example of Na+,CO32-–НАР. The higher antagonistic effect was observed for sample with nanosized particles.
Synthesized phosphates inhibit the biofilm formation by Staphylococcus aureus and Pseudomonas aeruginosa, and their activity depends on the ability to adhere to the surface of bacteria cells.
Hybrid composites on the base of synthesized Cu2+, Zn2+ and Cu2+/Zn2+-containing apatite type calcium phosphates and alginate were created. Improvement of their mechanical properties comparing with those for phosphate component was shown.
